Defensa de la tesi doctoral, Ferran Romero. Multiple stressor effects on river biofilm communities: from community composition to ecosystem processes using experimental mesocosms

11h. Sala d’actes ICRA

Defensa Tesis: Multiple stressor effects on river biofilm communities: from community composition to ecosystem processes using experimental mesocosms

A càrrec de:  Ferran Romero

Directors de tesi:  Sergi Sabater(ICRA i UdG) i Vicenç Acuña (ICRA)

abstract:

Human activity worldwide exposes aquatic ecosystems to multiple anthropogenic stressors. Freshwater ecosystems are of special concern because of their notable sensitivity to stressors and relevance for global biodiversity and human well-being. Among the many stressors that threat freshwater ecosystems, those derived from land-use change include the release of many pollutants into rivers and streams flowing through urban and agricultural areas. Also, climatic stressors such as warming, and others related to human action such as hydrological stress, affect river ecosystems on a global scale by modifying biodiversity patterns and ecosystem functioning. Among the many organisms exposed to multiple stressors in freshwater ecosystems, those attached to river and stream sediments play a crucial role in virtually all major ecosystem processes and are frequently used as sentinels when assessing stressor impacts on freshwater ecosystems. This thesis aims to identify the single and multiple-stressor effects of warming, hydrological stress and pollutant exposure on river biofilms. To that purpose, I used several experimental approaches, consisting on glass crystallizers and artificial streams to expose river biofilms to single and multiple-stressor scenarios under controlled conditions. I tested the river biofilm response both at the structural and the functional scale, employing response variables that ranged from photosynthetic and enzymatic activity to gene expression and bacterial community composition. I detected that hydrological stress was the most influential stressor, specially impairing the biofilm community growing on cobbles. Water warming had lesser effects, mostly affecting bacterial activity due to the dependence of metabolic activity on temperature, but showed limited effects on bacterial community composition. Pollutant exposure had contrasting results depending on the nature of the pollutant used. The results presented in this thesis show that single and multiple stressors affect both biofilm community structure and function, and emphasize that river biofilms show an adaptive nature when facing multiple-stressor scenarios.